Originally Posted by Ironflight
I get really nervous when I see this many people say "run a tap through your nut plates!" Sure - there are a few low risk places where this might be OK. But airplanes are not cars, trucks, boats, or houses - fasteners in aircraft are designed to be hard to remove because the consequences of critical parts coming off are much worse than getting stuck by the side of the road. Cavalierly telling people to "run a tap through" defeats the locking purpose of the fastener, and while that might be OK on a storage compartment inside the cockpit, it is not such a good idea on a fuel tank attach plate.
The problem with blanket advice like this is that some places, its OK, other places, it is dangerous, and a rookie builder probably might not know the difference. But its the easiest way to go, so they listen to this large number of people on the internet, rather than the designer of their airplane, or the good words in the good book of acceptable techniques and practices (AC 43.13).
The bottom line is that if you use good tools, and you use BoeLube (beeswax is a good substitute if you check the ingredients) the first time you put a screw in a new nut plate (both recommended by experienced designers and the makers of most kits), you shouldn't have problems. Randomly removing the locking feature of aircraft fasteners is just a bit careless, and a shortcut to doing things right. And shortcuts often lead to bad places.
Dogfight! (yeah, I know, that's the other
First, auto and truck fastener failures have life and death consequences, just like airplanes. However, you won't find a lot of locking fasteners, because fastener loss just isn't much of a problem. If it was, believe me, the NHTSA would make the FAA look like Boy Scouts, not to mention the truck crash lawyers behind every tree.
"Designed to be hard to remove"? Not really. Nutplates were designed to be reliable (read "don't turn") blind thread receptacles. The locking function is secondary, and can be a plastic insert, which has nothing like the friction of an "egg hole" all metal plate nut. And if high friction is critical, should we ban rivnuts? Zeus fasteners? Quarter turn cowl hardware?
Let's take a hard look at the applications on an RV. There are a few places where a plate nut is used in structure, but they're typically 3/16 and 1/4", and get torqued bolts. There are also the tank screws, along the front spar. None get removed short of a serious issue, so sure, why fool with the locking feature?
The vast majority hold inspection plates, floorboards, seat parts, etc...stuff removed for inspections at least one per year. All have multiple screws. The loss of a single screw means zip, and even if the part managed to shed enough screws to actually come adrift, how many would be critical to the continuation of flight? Bottom line is that there is no good reason why removing them should be hard. We might even argue that making removal hard just encourages pencil annuals, while easy removal supports inspections.
Last, it is entirely possible to tweak an all-metal K1000 with a tap so it has plenty of lock left in it, but not enough to strip a screw head. There is no reason to ban a tap when used sensibly.